Can I be the same user on all Discourse forums?
We do offer a preliminary but functional global nickname registration. If you want to be consistently known as @kittenbunny99 across all Discourse instances, you can. You'll also get a user page here that optionally lists all your forum memberships.

For now, sign up on meta and that will globally reserve your nickname for later use.

@whs, This is the only forum I belong to. Although I have visited others, never joined because I didn't like the set-up. Give it a chance, might turn out okay. If not you can always pass later. Just like many here sign-up, come on for awhile and you never hear from them again.